However, I do find the assertion that maxed volume on a source is best for quality pretty counterintuitive. If you think of a volume poteniometer as a car's throttle, it's pretty clear that it would interefere least when the pathway is wide open.

You've got that backwards. A potentiometer is a variable resistor, not an amplifier. When volume is at its lowest, it's got the most resistence in the signal path and when it's at its loudest, it's got the least resistence (or none at all) in the signal path.

You've got that backwards. A potentiometer is a variable resistor, not an amplifier. When volume is at its lowest, it's got the most resistence in the signal path and when it's at its loudest, it's got the least resistence (or none at all) in the signal path.

I must've phrased that badly. That the volume control offers the least interference when it's set at max makes perfect sense to me. What's counterintuitive is that the signal from an amp working as hard as it can, but with minimum effect from the volume pot, will be better than an amp working in its "comfort zone" despite a bit of distortion from the pot.

I can see, though, that there's an assumption in my thinking: I'm presuming that the volume control actually works as a throttle on the power of the amplifier (turning it up makes the amp work harder/play louder, and vice versa). If, however, in a DAP, the amp is always working at the same rate, and the volume control is providing attenuation "downstream," then my thinking is clearly wrong on this matter.

Is that the way it works? I'm pretty sure that on my home amp, the volume control is controlling the amount of current supplied to the amplifier, and not just providing resistance. But I have no good reason to assume that a DAP would be designed the same way...

Is this why recommendations that I've seen say use the DAP at 75% or so volume if you drive an amp from the headphone out. To provide a good signal to noise ratio while keeping distortion levels down?

Well put! Many folks say, "use max volume," but others say "use 80%, so as to keep the amp from distorting from overwork." Intuitively, I agree with the latter, because my experience with turning car & home amps all the way up has been that they always distort (and badly) at maximum output and with a dynamic or bass-heavy source. This thread has really made it seem to me as though an amped LO that uses max volume would only be better than an HO under certain circumstances:

1) a very noisy volume control acting as a throttle on output signal is "'downstream" from the amp, on the circuit path to the HO (but not to the LO).
2) distortion-inducing DSP/EQ circuitry is bypassed when the LO is used.
3) the HO jack itself, or its internal connectors, is very low quality
4) the amp is of such quality -- or conservative design -- that it simply cannot distort at any power level.

Since the many reports of high sound quality available through the iPod LO cannot be gainsayed, I'm wondering whether one or more of these conditions applies to the iPod. I also wonder if anyone has done a comparative listen between, say, an iPod classic and a Zune80...

And thanks to all the contributors here - this has been a really educational thread for me.

For me, the combination of listening to a wide range of music and the relative weakness of the onboard iPod headphone amp means that I can't get enough volume. Older music that hasn't been compressed to within an inch of its life is rarely loud enough on its own if you're using anything that's hard to drive.

Elladan, another thing that is different on the Ipod is the fact that sometimes, (especially bass heavy stuff) you get distortion via the ho at full whack. The amp seems to have lost its control. However, the lo is louder and cleaner!!

This suggests something is in line via ho. I'm using an EU Ipod so the volume has been limited, but even so, I can get it to distort at high volume on occasions.

Ian -- I suspect you're right, and that it's the DSP/EQ circuitry to blame. One wonders if that's why MS elected not to include an EQ. I viewed it as a potential negative at the time of my purchase, but trusted the Zune's reputation for good sound quality. Hmmm.

This has definitey been an interesting thread. But to return to the original question: "what's the point?" Sure, you're amping a signal that's been amped, but there are two benefits: 1) by providing more current, you're making it easier for your headphones/IEMs to do their job, and 2) the sound signature of the amp can improve the signal, even if it's inherently poor. In the best case, the amp's characteristics can compensate for an amp's failings. It won't be absolutely hi-fi, but it can be better than listeninng straight from the source. Conversely, of course, an amp could accenctuate a source's failings. This thread has probably run its course, but i wonder if anyone has experienced that.

for me it would be #2, but I see people amping already amped sources, I honestly don't see the point of that, you're amping an already amplified source :X but then people will argue that if you set the DAP's volume to a certain volume it will act sort of like a line out, which in theory still shouldn't be as clean as a proper line out, which defeats the whole purpose of amping in the first place.

You are making the incorrect assumption that the better quality components & better designed circuit of the portable amp doesn't clean up the non-music artifacts introduced in the barely sufficient original amplification stage. Here's a news flash bulletin ; It does that in spades w/ a good amp. The noise floor is greatly lowered & there is an appreciable gain in musical information. My take is that I think a lot of listeners would be pretty supprised that the sound from the amp is not just an amplified clone of the original sound. I am absolutely positive that I really don't care to listen to any of my DAPs un-amped or use IEMs anymore, although even IEMs benefit from amping.

I have a Zune 80 and UE-11 Pro's. There is little hiss, but the hard disk spinning (And I'm starting to expect even more than just that) make up for it, deliviring a very annoying bunch of sounds. I use a Shure resistor thingy, with the volume wheel on it, to lower the hiss. I turn the player to almost (Not completely because I can't attenuate enough like that, UE-11's are sensitive!) max volume, and then seriously lower the volume with the resister/attenuator.

It works because the noise (Hard disk) gets lowered as well as the music, making it all inaudible to me!

There's absolutely no noise floor on my Tomahawk being fed by my iPhone (through the iPhone headphone out at that!). I have my iPhone volume turned up to one notch before maximum volume. The only thing I found with the Tomahawk is if your input signal is pass a certain point and then you try to push the little amp to and past around 3 o'clock on the knob it will tend to clip/distort. This is probably from the amp trying to pump out more current than the two AAA batteries could handle (also drains the batteries extremely quickly). However, again, no noise floor and with it being connected to a iPhone, the EMF interference is kept to a very very very minimum, in other words the noise from EMF interference will not come anywhere near to blowing out your eardrums like some other amps would.

I have a Zune 80 and UE-11 Pro's. There is little hiss, but the hard disk spinning (And I'm starting to expect even more than just that) make up for it, deliviring a very annoying bunch of sounds. I use a Shure resistor thingy, with the volume wheel on it, to lower the hiss. I turn the player to almost (Not completely because I can't attenuate enough like that, UE-11's are sensitive!) max volume, and then seriously lower the volume with the resister/attenuator.

It works because the noise (Hard disk) gets lowered as well as the music, making it all inaudible to me!

But I still want an amp, something small and quality...

I had both problems w/ my Zune 80 & UM2s. I added a Total Airhead to the mix & the problems disappeared. I think the analog stage in the Zune isn't up to snuff w/ higher sensitivity IEMs & it passes thru artifacts that are not part of the music signal generated by the Zune. That is probably the reason that most DAPs come w/ generic earbuds. It kind of suprised me that most if not all of the drive noise isn't audible w/ the Zune set to full volume. High frequency hiss is completely gone which is what leads me to believe the amp is completing the analog stage left unfinished by the Zune.